In a wafer-level lens process in which a plurality of lenses is arranged in a plane direction of a wafer substrate, it is difficult to obtain the shape accuracy or the position accuracy when the lenses are formed. In particular, it is very difficult to perform a process in which wafer substrates are stacked to manufacture a stacked lens structure, and stacking of three layers or more is not realized in mass production level.
Various techniques related to the wafer-level lens process have been devised and proposed. For example, PTL 1 proposes a method in which when a lens material is filled into through-holes formed in a substrate to form a lens, the lens material itself is used as an adhesive to stack wafer substrates.